This application claims priority to an application entitled xe2x80x9cRoute Guiding Method for In-Vehicle Navigation Devicexe2x80x9d filed in the Korean Industrial Property Office on May 3, 2001 and assigned Serial No. 2001-24166, and to an application entitled xe2x80x9cRoute Guiding Method for In-Vehicle Navigation Devicexe2x80x9d filed in the Korean Industrial Property Office on Mar. 18, 2002 and assigned Serial No. 2002-14428, the contents of both of which are hereby incorporated by reference.
1. Field of the Invention
The present invention relates generally to a navigation device, and in particular, to a route guiding method for an in-vehicle navigation device.
2. Description of the Related Art
Navigation using satellite signals was first used for aircrafts and nautical vessels, and is now becoming more widespread in other vehicles, such as cars, trucks, busses, motorcycles, etc. As vehicles are being equipped with in-vehicle navigation devices using satellites, many techniques are being developed to track the vehicles more precisely. Such an in-vehicle navigation device receives data about the position of a vehicle from the satellites, reads map data from a device in the vehicle, and pinpoints the shortest route on the map visibly and audibly for a user. The route guidance function is fundamental to the in-vehicle navigation device. After an optimum route to a destination is calculated, when a vehicle is traveling and an intersection is in sight, information about the intersection is provided to the user. The guidance information about the intersection is provided to the user by voice and with a related image when the vehicle reaches a specified point (e.g., 100 or 300 m ahead), alerting the user of the direction he is supposed to turn at the intersection beforehand.
The conventional in-vehicle navigation device, however, confuses the user by providing guidance information about a next intersection during turning at an intersection or providing scheduled intersection information to the user when the user""s vehicle is off track.
It is, therefore, an object of the present invention to provide an improved route guiding method for an in-vehicle navigation device.
It is another object of the present invention to provide a route guiding method that eliminates the confusing situation where guidance information about the next intersection is provided during successive intersections or when a vehicle is off track.
The foregoing and other objects are achieved by providing a route guiding method for an in-vehicle navigation device. To guide a vehicle to a destination by an optimum route, it is determined whether the vehicle is on track within a predetermined intersection range based on route guidance data received from a traffic information center via a mobile communication network. If the vehicle is on track within the intersection range, it is determined whether the vehicle is in a free run state according to predetermined free run conditions preventing a preliminary route guidance message that is confusing to a driver in the free run state. According to the determination result, the preliminary route guidance message is selectively provided.
The free run conditions include coincidence between the direction the vehicle is pointing and the direction of a calculated route, the azimuth difference between a road that the vehicle takes and the other roads at an intersection, the distance the vehicle moves from the intersection, and the distance between the current intersection and a next intersection.